The objective of this experiment was to determine the effects of replacing coastcross hay (Cynodon sp.) by soybean hulls on nutrient apparent digestibility, ruminal measures and nitrogen metabolism. Sixteen ram lambs (40±5 kg of body weight) were housed individually in metabolism crates and assigned to a randomized completely block design. The experimental period consisted of 14 days; the first 10 days were used to adapt lambs to treatments and 4 other days for data collection. Animals were fed diets containing 50% concentrate and 50% roughage, both with the same amount of neutral detergent fiber (NDF). Soybean hulls replaced coastcross hay by 0, 33, 67 or 100% in the dry matter. Dry matter (DM) intake and NDF showed quadratic effect when soybean hulls were added to the diet. However, DM and NDF digestibility increased, while short-chain fatty acids, acetate and propionate concentration did not change and ruminal pH and ammonia decreased. Partially replacing coastcross hay by soybean hulls increases DM intake and lowers ruminal pH without affecting DM or NDF digestibility.